High temperature valve



R. D. MCKENZIE HIGH TEMPERATURE VALVE Filed Dec.l ll. 1961 NN \NINVENTOR OBEPT D. McKENZ/E ATTORNEY Aug. 20, 1963 QR liflwl UnitedStates Patent O 3,101,694 111GB TEMPERATURE VALVE Robert ll). McKenzie,East Hartford, Conn., assigner to United Aircraft Corporation, EastHartford, Conn., a

corporation of Delaware Filed Dec. 11, 1961, Ser. No. 158,397 1 Ciainl.(Cl. 137-340).

This invention relates to an improved valve structure and moreparticularly to fluid-tight valving' for high vacuum for extremetemperatures. v y

ln fluid systems wherein high vacuums are involved, the fluid-tightsealing of valving in the system is critical. When operating withvacuums in the order of ld5 to 1(1"9 mm. Hg, or lower, it is necessaryto elevate the temperature of the parts involved so as to drive oil anyvgas molecules which may have been absorbed on the metal surfaces exposedto the vacuum. Therefore, it 1s necessary to provide valves in thesystem which can operate through a number of sequences and which canprovide fluid-tight sealing at elevated temperatures as well as at roomtemperature.

It is therefore an object of this invention to provide a valvecomprising la metal seat and piston which cooperate to provide thehuid-tight seal by virtue of an interference tit between lthe two. lnspite of this interference liit this valve is so arranged that it iscapable of repeated operation without appreciable wear or distortion.

VThese and other objects of this invention will become readily apparentfrom the ifollowing detailed description of the drawing, in which:

FlG. l is a detailed cross section of the valve in its open position;and

IFIG. 2 is a sectional view of the Valve in its closed position.

Referring to FIG. l, a valve body 1t) includes an inner chamber 12 and amachined bore 14. The sidewall of the bore 14 is slightly tapered. Thebody 10 includes an inlet 18 and an outlet 2t). A reciprocable valvepiston element 24 is located within the chamber 12. The sidewalls 26 ofthe piston 24 also include a slight taper which substantially conformsto the taper of the wall 16 in the bore 14. The valve piston 24-includes an annular ilange Z3, to which is brazed a metal bellows 30.The brazing or other suitable sealing connection is made at 32 toconnect the lower end of the bellows 3d and the upper sunface of theflange 28. r[The upper end of the bellows 30 is suitably connected at 34to a cap or bushing member 36.

The stem 4d of the valve piston 24 has a substantially close fit as at42 with the bushing 36. The bellows connection between member 36 andseal 34 is such that the valve piston 24 is able to move vertically, butwill not rotate about its longitudinal axis. The valve stem 4t? includesa threaded-portion 5@ which is engaged by a nut 52. An annular cap 54 isbolted to the body 10 and includes a lip 56 engaging the llange 58,`forming the lower portion of the nut 52. lt will be noted that rotationof the nut 52 will cause the valve stem 40 and piston 24 to movevertically.

The valve piston 24 is preferably made of a relatively soft metal havinga high coeiiicient of expansion, e.g. copper. The valve body andparticularly the seat as delined by the bore 114 is preferably of a hardmetal such as steel which, as compared to copper, has a lower therrnalconductivity and lower coeiiicient of expansion.

ln order to operate the valve, a cryogenic liuid, as 'for example,liquid nitrogen, is supplied frompa source 62 whereby it iiows throughvalve v64, and to the passage 66 which leads to the chamber 68 in thehollow portion of the valve piston 24. The cryogenic uid (liquidv nitro-3,101,094 Patented Aug. 270, 1963 gen) will shrink the valve pistonsuiciently so that it can be moved to the position shownin'FlG. 2 bymeans-of rotation of the nut in FIG. 2. In this position the piston- 24lits snugly into the bore 14 and becauseof the taper of the sidewalls ofthe pistony and the bore, a close tit will be obtained. After the valveis moved to this closed' position the valve 64 is closed and valve'70opened to vent the nitrogen from the` chamber 68. As a result, the valve.piston 24 will reach the ambient temperature, expanding at a greaterrate than the surrounding steel body such that an interference t,resulting in an extremely rrn, duid-tight seal is provided, therebypreventing the flow of any huid between the conduits 18 and 20. Ifn thisposition the bellows 3i)` will prevent any ilow of fluid up past thevalve stem 40 and the soft metal ring seal 7 6 between the body 10 andthe bushing -36 prevents any huid escape past the engaging surfaces inthe last mentioned parts.

In the closed position, the valve can be exposed to wide rangesottemperature change without losing any of its sealing capacity. Thediifering coefficients of expansion of the metals of the piston and seatcontribute to the seating .and unseating of the valve. During theopening operation, the valve piston will be `freed from the seatrapidly, allowing the piston to be withdrawn with no actual slidingcontact with the seat walls, thus eliminating wear.

As mentioned above, in order to insure the high vacuum desired, it isnecessary to bake the various parts or, 1n other words, raise theirtemperature to insure that the gases absorbed in the metal surfaces aredriven olf. This baking insures that the gas molecules are not laterfreed to contaminate the vacuum system. Although the valve may withstandbaking while open or closed, it normally would be exposed to hightemperature in its open position during the pumping down of the system.

In order to open the valve, the vent valve 70 is closed while the supplyvalve `64 is opened to again lill the charnber 58 with liquid nitrogen.This lowers the temperature of piston 24 and causes it to shrinkslightly. By turninlg the nut 52, the piston 24 can be withdrawn fromthe bore 14 with ease and without any damage to the engaging parts. Itis important to note that since the copper piston of the valve is soft,it readily conforms to the suri'ace of the bore when its temperature iselevated following the release of the nitrogen from the chamber 68. As aresult the valve can be used repeatedly and is not subject to wearing orgalling, or the deterioration commonly existing in high temperaturevalves utilizing ordinary seating devices.

As a result of this invention it will be apparent that a very simplevalve structure has been provided which is reliable under extreme vacuumconditions.

Although only one embodiment of this invention has been illustrated anddescribed, it will be apparent that various changes and modications maybe made in the arrangement of the various parts without departing fromthe scope of this novel concept.

7 I claim:

A valve adapted to provide a fluid-tight seal at elevated temperaturesand under high vacuum conditions comprising a body, a tapered bore insaid body forming a relatively hard metal valve seat having a hardnessof the order of steel, a movable valve element of frustoconical shapeengageable with said seat and having a tapered sidewall portion shapedto generally conform to said seat, a iiuid tight bellows connecting saidbody and element, said valve element being vformed of a relativelysoftmetal having a hardness of the order of copper, said latter metalhaving a higher coefficient of expansion and 4 a higher thermalconductivity than the metal valve seat, References Cited in the le ofthis patent a chamber in said valve element including a passage con-UNTTED STATES PATENTS nected thereto, a source of cryogenic fluid, meansIfor 685 748 Davis NOV 5 1901 conducting said fluid to said passageandsaid chamber to 2,114139 CmSthQt-:n: Apr '12 1938 Vshrink said elementat a rate relatively greater than the 5 132262 Gabriel Oc't. 4 1938adjacent seat, means, 'for moving said valve element into 2,919,710VLantz Jan 5 1960 engagement with said seat, means for venting said pas-2,994,333 Wilson Aug. 1, 19611 sage and chamber whereby after engagementwith said 3,028,874 Burkett APL 1()I 1962 seat the said valve elementexpands at the operating temperature of the -valve to form aninterference t with said lo )THER REFERENCES h s eat and the soft metal.wall of said element readily con-VV T001 Engmeermg Fell 1958 (AS'T'E-Chlcago): Pages forms to the contour off said seat. f v 107-115" Page112 relied on'

